Flexible versions of products and components that are traditionally rigid in nature are being conceptualized for new applications. For example, flexible electronic devices can provide thin, lightweight and flexible properties that offer opportunities for new applications, for example curved displays and wearable devices. Many of these flexible electronic devices require flexible substrates for holding and mounting the electronic components of these devices. Metal foils have some advantages including thermal stability and chemical resistance, but suffer from high cost and a lack of optical transparency. Polymeric foils have some advantages including resistance to fatigue failure, but suffer from marginal optical transparency, lack of thermal stability and limited hermeticity. Polymeric foils also suffer from a limited ability to offer impact-resistance to underlying electronic components. Further, polymeric foils can suffer from permanent deformation associated with their viscoelasticity upon repeated application-related bending.
Some of these electronic devices also can make use of flexible displays. Optical transparency and thermal stability are often important properties for flexible display applications. In addition, flexible displays should have high fatigue and puncture resistance, including resistance to failure at small bend radii, particularly for flexible displays that have touch screen functionality and/or can be folded.
Conventional flexible glass materials offer many of the needed properties for flexible substrate and/or display applications. However, efforts to harness glass materials for these applications have been largely unsuccessful to date. Generally, glass substrates can be manufactured to very low thickness levels (<25 μm) to achieve smaller and smaller bend radii. These “thin” glass substrates suffer from limited puncture resistance. At the same time, thicker glass substrates (>150 μm) can be fabricated with better puncture resistance, but these substrates lack suitable fatigue resistance and mechanical reliability upon bending.
In addition, foldable glass substrates for foldable electronic device applications, while offering improvements in transparency, stability and wear resistance over polymeric foils, can be limited by impact resistance. More particularly, impact resistance concerns for foldable glass substrates can be manifested in damage to the substrate and/or underlying electronic components when subjected to impacts.
Thus, there is a need for improved foldable electronic device assemblies, and cover elements for these assemblies, for reliable use in flexible substrate and/or display applications and functions, particularly for flexible electronic device applications.